<style>
#container .koukou .chuangkou {
  width: 400px;
  height: 400px;
  background: url(../images/qq.ll.jpg) no-repeat center center;
  position: fixed;
  left: 36%;
  top: 25%;
  border-radius: 8px;
  z-index:2;
}

#container .koukou .chuangkou .guanbi {
  display: block;
  width: 50px;
  height: 20px;
  position: absolute;
  right: 0;
  top: 0;
  cursor: pointer;
  background: skyblue;
  text-align: center;
  border-top-right-radius: 8px;
}

#container .koukou .chuangkou h4 {
  font-size: 25px;
  color: black;
  text-align: center;
  font-weight: normal;
}

#container .koukou .chuangkou form {
  width: 300px;
  height: 200px;
  margin: auto;
}

#container .koukou .chuangkou form input {
  width: 295px;
  height: 40px;
  margin-top: 30px;
  border-radius: 8px;
  padding-left: 5px;
}

#container .koukou .chuangkou .btn {
  display: block;
  width: 250px;
  height: 30px;
  background-color: teal;
  border-radius: 8px;
  border: none;
  outline: none;
  cursor: pointer;
  margin: auto;
}
</style>

<div class="chuangkou">
        <span class="guanbi" id="guanbii">X</span>
        <h4>欢迎登陆</h4>
        <form action="#">
          <input type="text" placeholder="请输入QQ号/手机号" class="nums">
          <input type="password" placeholder="请输入密码" autocomplete='tel' class="pwd">
        </form>
        <button type="button" class="btn">登陆</button>
      </div>
    </div>